(1) Field of the Invention
The present invention relates to an organic photosensitive material for electrophotography. More particularly, the present invention relates to an improvement in a photosensitive material comprising a polyvinyl carbazole type charge-transporting medium and a perylene type charge-generating pigment dispersed in said medium, wherein the sensitivity is increased and the fatigue at the repeated light exposure is prevented.
(2) Description of the Prior Art
As the conventional single-layer type photosensitive material comprising a charge-transporting medium and a charge-generating pigment dispersed therein, there is known a photosensitive material comprising a phthalocyanine type or dis-azo pigment dispersed in a medium composed mainly of polyvinyl carbazole. However, it is admitted that a photosensitive material comprising a perylene pigment dispersed in polyvinyl carbazole (hereinafter referred to as "PVK") has no practically applicable sensitivity.
It is known that various sensitizers may be incorporated so as to sensitize a photosensitive layer comprising a charge-generating pigment dispersed in a charge-transporting medium. However, when these known sensitizers are applied to the combination of PVK and the perylene pigment, most of these known sensitizers are still insufficient in the sensitivity and the charge potential or the adaptability to the repeated light exposure.
We already found that a halo-naphthoquinone has a substantially satisfactory sensitizing effect to the PVK-perylene pigment combination. However, a photosensitive material in which this halo-naphthoquinone is incorporated is still insufficient in that the fatigue at the repeated light exposure, that is, the light memory effect, is extreme and the initial saturation charge voltage is drastically reduced on the surface of the photosensitive material by the repeated light exposure.